Stringed musical instrument



Apfll 4, 1939 G. D, BEAUCHAMP STRINGED MUSICAL INSTRUMENT Filed May 26, 1956 2 Sheets-Sheet 1 April 4, 1939-, G. D. BEAUCHAMP 2,152,733

STRINGED MUSICAL INSTRUMENT Filed May 26, 1936 2 Sheets-Sheet 2 g /4 NW5 /5 (E2912 AT Patented Apr. 4, 1939 UNITED STATES PATENT OFFICE STRINGED MUSICAL INSTRUMENT ifornia Application May 26, 1936, Serial No. 81,826

15 Claims.

This invention relates to musical instruments and relates more particularly to stringed musical instruments. A general object of this invention is to provide a practical stringed musical instru- 5 ment embodying simple, novel means for producing a tremolo effect.

Another object of this invention is to provide a stringed musical instrument embodying a shiftable bridge on which the vibratory strings bear and means for shifting the bridge to create quavering or tremulous tones.

Another object of this invention is to provide a stringed musical instrument of-the character mentioned in which the shiftable bridge is movs able longitudinally or in the direction of the strings as well as in a direction transverse of the strings to produce a pleasing tremolo effect with little or no variation in the tension on the strings.

Another object of this invention is to provide a stringed musical instrument embodying an effective means. for producing a tremolo effect that may be conveniently operated or manipulated by the musicians hand employed to pluck o-r vibrate the strings.

Another object of this invention is to provide a stringed musical instrument of the character mentioned that is operable to produce a pleasing tremolo effect without noise and rattle and without varying the pitch of the vibratory strings beyond a desirable range of variation.

Another object of this invention is to provide a means for creating a tremolo elfect in a stringed musical instrument that is suitable for embodiment in or application to an instrument embodying an electro-magnetic pick-up.

Another object of this invention is to provide a stringed musical instrument embodying means for varying the effective lengths of the several strings to create a tremolo effect on the several strings of the instrument.

A further object of this invention is to provide a. device or appliance for producing a tremolo effect in a stringed instrument that is. compact and inexpensive and that may be easily embodied in or applied to various types of stringed instruments.

The various objects and features of my invention will be fully understood from the following detailed description of typical preferred forms and applications of the invention, throughout which description reference is made to the accompanying drawings in which:

Fig. 1 is a plan elevation of an instrument embodying one form of the invention. Fig. 2 is an enlarged fragmentary vertical detailed sectional view taken as indicated by line 2-2 on Fig. 1. Fig. 3 is a transverse detailed sectional view taken as indicated by line 33 on Fig. 1.

Fig. 4 is an enlarged fragmentary detailed sectional view taken as indicated by line 4-4 on 5 Fig. 2. Fig. 5 is a fragmentary plan elevation of an instrument embodying another form of the invention. Fig. 6 is an enlarged transverse or vertical detailed sectional view taken as indicated by line 66 on Fig. 5, and Fig. '7 is an enlarged fragmentary vertical detailed sectional view taken as indicated by line 'I--I on Fig. 6. The means or apparatus provided by the present invention for creating a tremolo effect may be embodied in or applied to stringed musical instruments of various characters, for example, it may be used on banjos, guitars, mandolins, harps, pianos, etc., with or without pick-up means. In the following detailed description I will describe two typical forms of the invention as em- 9 bodied in a guitar having an electro-magnetic pick-up of the character described and claimed in my co-pending application entitled Electrical stringed musical instrument, Serial No. 728,717, filed June 2, 1934. It is to be understood that the invention is not to be construed as limited or restricted to the specific forms or applications about to be described.

The instrument of the present invention illustrated in Figs. 1 to 4, inclusive, of the drawings, includes generally, a body Ill, a plurality of vibratory strings II on, the body Ill, a stationary inner bridge I2 for certain of the strings I I, a movable inner bridge I3 for the other strings I I, means I4 for moving the bridge I3 to produce a tremolo effect, and an electromagnetic pick-up. I5 responsive to or influenced by the strings II and operable to impose electrical modulations on an amplifying and speaker circuit to produce the tones of the vibratory strings II.

The body I0 may be varied in construction and design without departing from the invention. In the typical embodiment of the invention illustrated in the drawings the body Ill is formed of Bakelite or the like, and has the general configuration of the usual guitar type of instrument. In practice the body In may be solid or integral and may be provided with several cavities I6 closed by ornamented or ornamental plates II. The usual neck I8 projects from the body I!) and 50 is provided at its outer end with a peg box portion I9. A suitable fingerboard 20 is provided on the neck I8 and has the usual frets 2!. In accordance with the invention an opening or recess 22 is provided in the upper side of the body. 55

The recess 22 extends longitudinally of the body III and the strings II and has vertical or parallel side walls and an inclined bottom wall 23. The bottom wall 23 of the recess 22 is inclined downwardly and rea-rwardly as illustrated in Fig. 2. In the particular form of the invention being described the recess 22 is at one side of the central longitudinal axis of the body ID. A transverse opening 24 is provided in. the upper side of the body I9 to carry the pick-up I5. The opening 24 is spaced forwardly of the recess 22 and intersects the central longitudinal axis of the body I0 and the series of strings II.

The strings II are the tone producing or the tonal vibration producing elements of the instrument. Certain of the strings II may be of steel and the other strings may be the usual metal wound strings employed on guitars and the like. The strings II extend longitudinally across the fingerboard 29 and the upper side of the body III. The inner portions of the strings II extend through substantially vertical openings 25 in the body I9. Sockets 26 in the bottom of the body II) joint the openings 25. The usual spools 21 on the ends of the strings II cooperate with the bottom. walls of the sockets 26 to anchor the inner ends of the strings II to the body III. A tail piece ridge 28 projects from the upper side of the body II) at the rear end of the recess 22. The strings II bear on and pass forwardly from the ridge 28. The string receiving openings 25 and sockets 26 and the ridge 28 eliminate the necessity for the usual tail piece for anchoring the inner ends of the Vibratory strings II.

The strings II are arranged in spaced relation in a substantially horizontal series. In the particular instrument illustrated there are six spaced strings, it being understood that there may be more or less strings, as desired. The strings II are graduated in diameter and those of small diameter may be of steel and those of larger diameter may be wrapped in the usual manner. Keys or pegs 29 are provided in the peg box portion IQ of the neck l8 to tension the strings II. The strings II pass over and bear on a fixed bridge 3|] at the outer end of the neck I8 and pass from the bridge 30 to the pegs 29. It is believed that it will be apparent how the strings II may be tensioned and tuned by means of the pegs 29.

The stationary bridge I2 is provided on the body I9 to be engaged by the bass strings or the heavy strings of the instrument. In the particular case illustrated three of the strings II bear on the relatively stationary bridge l2 and three of the strings bear on the movable bridge I3. The stationary bridge I2 is spaced forwardly from the tailpiece 28 being opposite or at the inner side of the recess 22. If desired the bridge I2 may be an integral projection or part of the body I9. As illustrated, however, the stationary bridge I2 is a separate part secured to the body I9 by suitable screws 3|. The upper end of the bridge I2 is shaped for engagement by the strings II. In the case illustrated the upper end of the bridge I2 is in the nature of a relatively narrow ridge having notches 32 for receiving the strings II.

The movable bridge I3 is engaged by the three lighter or smaller strings I I and is movable in the recess 22 to produce a tremolo effect during vibration of the strings. The bridge I3 is preferably in the form of a roller, drum or wheel and is adapted to be rolled longitudinally in the recess 22 by the operating means I4. The movable bridge I3 includes a roller 33 cooperating with or forming a bridge support for the strings II. The roller 33 is cylindrical having a cylindric exterior for shiftably engaging the three strings ll. The roller 33 is smooth and accurately finished to have a minimum of friction in its engagement with the strings.

In accordance with the invention anti-friction bearing means are provided to support the roller 33 for free movement in the recess 22. trunnions 34 project from the opposite ends of the roller 33. Inner rings or races 35 are rotatable on the trunnions 34. Outer races 36 surround the inner races 35. The opposing surfaces of the races 35 and 36 are suitably grooved to receive a series of balls 31. The races 35 and 36 preferably have fiat ends for cooperating with the side walls of the recess 22. The outer races 38 have cylindrical peripheries for rolling on the inclined bottom wall 23 of the recess 22. The assemblies of the races 35 and 36 and the balls 31 form effective anti-friction wheel elements for supporting the opposite ends of the roller 33 in the recess 22. The outer ends or sides of the races 35 and 35 are adapted to cooperate with the side walls of the recess 22 to prevent or limit endwise movement of the bridge I3. The bridge I3 is formed and proportioned to have the upper surface of the roller 33 above the plane of the ridge 28 so that the tensioned strings II bear on it at all times. When the movable bridge I3 is at the forward end of the recess 22 its central longitudinal axis is longitudinally aligned with the stationary bridge I2. A stop 38 of felt or the like is provided at the forward end of the recess 22 to limit the forward movement of the bridge 23. It will be observed that the position of the bridge roller 33 in the recess 22 in efiect deter mines the effective lengths of the strings or the lengths of the tone producing portions of the strings II bearing on the bridge I3. Movement of the bridge I3 in the recess 22 therefore varies the elfective length of the three strings II en gaging the bridge.

The means I4 for moving or shifting the bridge I3 is conveniently operable by the musician to vibrate or move the bridge I3 back and forth as he plucks or otherwise vibrates the strings.

, The means I4 includes a pivoted lever 39. The

lever 39 may be pivotally supported on the body II] in any practical manner. In the particular case illustrated in the drawings, the lever 39 has an arm or finger 49 pivotally carried in an opening M in or adjacent the outer end part of the bridge I2. A nut 42 or other suitable means may upper sides of the strings II engaging on the movable bridge I3. The lever 39 carries or operates a yoke 43 which cooperates with the roller 33. A pin 44 projects from the lever 39 and is shiftable and pivotable in an opening 45 in the yoke 43. A spring 46 surrounds the pin 44 and is arranged under compression between the lever 33 and the yoke 43 to hold the yoke in proper engagement with the roller 33. The yoke 43 is shaped to engage about the cylindric periphery of the roller 33 to impart movement to the bridge l3 when the lever 39 is pivoted.

The lever 39 is provided with a handle or actuating arm 41. The arm 41 projects forwardly at the outermost side of the series of strings I I relative to the musician. The outer end of the oper- Axles or T ating arm 41 is located to be adjacent the hand with which the musician plucks or vibrates the strings A head or knob 48 may be provided on the forward or outer end of the arm 41 to be engaged by the musician. The knob 48 is such that it may be received in the under side of the hand to be easily gripped or grasped by the small fingers. It is preferred to provide means for holding the movable bridge l3 in a normal position to facilitate tubing of the instrument and to permit playing of the instrument without creaating a tremolo effect. The means for holding the bridge |3 in a normal position may be in the form of a spring means. An arm 49 projects from the operating lever 39. A spring 50 is attached to the arm 49 and has an end suitably attached to the instrument body it. The spring 50 acts to hold the lever 39 in a position where the bridge roller 33 bears against the stop 38. When in this position the bridge I3 is longitudinally aligned with the stationary bridge I2. The spring 56 serves to hold the movable bridge I3 against movement in its foremost or normal position until the bridge is deliberately moved by the player to create the tremolo effect.

The pick-up I is in the nature of an electromagnetic pick-up means responsive to or actuated by the tone producing vibrations of the strings H to produce a modulated electric current which may be amplified and reproduced as the musical tones by a suitable amplifying and loud speaker unit. The particular pick-up l5 illustrated is of the type fully described and claimed in my co-pending application aboveidentified. The pick-up I5 is arranged in the opening 24 of the body and includes a pair of opposed permanent magnets M. The magnets M are of the horse-shoe type and are arranged in end to end relation with their corresponding poles in spaced opposition, as illustrated in Fig. 3. The magnets M are substantially horizontally disposed to have their lower arms 5| below the strings I and their upper arms 5| spaced above the strings The lower magnet arms 5| may rest on a plate 52 or electrical conducting nonmagnetic material. The plate 52 is-preferably adjustably supported in the opening 24 as will be subsequently described. The outer arms 5| of the magnets M extend transversely across the series of strings II in spaced relation thereto to carry the magnetic effect to the strings and to form a guard for the strings.

The pick-up |5 includes an induction coil C in the field of the pair of magnets M. The coil C comprises a spool 53 arranged between the inner and outer arms 5| of the pair of magnets M. The spool 53 is of suitable insulating and non-magnetic material and is oval or elongated in transverse cross section. The spool 53 is arranged to have its greatest transverse dimension extend longitudinally of the pair of opposed magnets M. A winding 54 of insulated wire is provided on the spool 53 to form the induction winding of the coil 0. The gauge of the winding 54 and the number of turns of the winding are determined by the type of the amplifier and speaker unit with which the instrument is to be used.

Core members, or magnetic pole members 55 are provided to concentrate the magnetic force in non-uniform fields linked with the coil C. The members 55 may be in the form of pins or rods. The lower ends of the members 55 engage the lower arms 5| of the magnets M. The members 55 extend outwardly through openings in the spool 53 to have their outer ends in spaced relation to the strings The upper ends of the members 55 are spaced directly below the strings One of the members 55 may be engaged by the inner winding of the coil C which is exposed to have electric conducting cooperating with the member. The inner end of the winding 54 is thus electrically connected with the plate 52. The pole members 55 operate to concentrate the magnetic force in spaced zones or fields in the spaces between the ends of the members 55 and the outer arms 5| of the magnets M. The strings pass through these concentrated magnetic fields and when vibrated vary the reluctance of the magnetic circuit to induce an electric current in the coil C.

The coil C is adapted to be electrically connected with a suitable amplifier and speaker unit (not shown) whereby the electrical current induced in the coil C by variations in the reluctance of the pick-up is imposed on the speaker unit to be converted into sound. The electrical current induced in the coil C has the frequencies and the other characteristics of the actual tone producing vibrations of the strings so that the tones produced by the amplifier and speaker unit are truly representative of the tonal vibrations of the strings. As amplifying and loud speaker circuits and units are well known to those skilled in the art and as various forms of such units may be employed with the instruments of the present invention the amplifying and speaker unit has been omitted from the present disclosure. A socket or jack 56 is provided on the body IU of the instrument to receive a plug from the amplifying and speaker unit. One lead or conductor 51 extends from the plate 52 to the jack 56 and a second lead 58 extends from the outer winding of the coil C to the jack 56 whereby the coil C may be electrically connected with a plug inserted in the jack 56. A suitable volume control 9 may be connected in one of the leads 5? or 58 to be conviently controlled by a knob B projecting from the upper side of the body It.

Means is preferably provided to adjust the pick-up unit relative to the vibratory strings II to obtain the desired operation of the pick-up. Pins 59 are fixed to the plate 52 adjacent its opposite ends and extend outwardly through openings 60 in the body l6. Washers 6| on the pins 59 bear on the upper side of the body l6. Nuts 62 are threaded on the pins 59 and bear against the washers 6|. The nuts 62 operate to adjustably support the plate 52 and the pick-up unit. Springs 63 surround the pins 59 and are arranged under compression between the washers 6| and the plate 52 to maintain the nuts 62 in proper engagement with the washers 6|. The nuts 62 may be simultaneously adjusted to bodily shift the pick-up |5 to move the ends of the members 55 toward or away from the strings I The nuts 62 may be individually manipulated to tilt or rock the pick-up unit l5 from one end or the other and thus obtain the desired adjustment of the pick-up.

It is believed that the operation of the instrument illustrated in Figs. 1 to l, inclusive, of the drawings will be readily understood from the foregoing detailed description. The strings may be plucked or vibrated in the usual manner and the vibration of the strings varies the reluctance of the magnetic circuit in the pick-up l5 to induce a current in the coil C which current is in turn converted into sound by the associated amplifier and loud speaker unit. If desired, the

instrument may be played without shifting the 7 bridge l3 and, therefore, without creating quavering or tremulous tones.

When it is desired to produce a tremolo effect in the tones produced by the three strings ll bearing on the bridge i3 the knob 48 is engaged or grasped to move or oscillate the arm 4']. As above described, the knob 48 may be conveniently rasped by the small fingers of the musicians hand with which he plucks the strings I l Vibration or movement of the arm 47 of course produces movement of the bridge 13 in the recess 22. As the bridge I3 is moved to and fro in the recess 22 the effective lengths of the strings ll bearing on the bridge 13 are changed or varied to make the tones produced by the strings quavering or tremulous. Due to the inclination of the bottom wall 23 of the recess 22 movement of the bridge l3 in the recess 22 is accompanied by minimum variation in the tension on the strings ll. Accordingly the tremolo effect is produced by varying the lengths of the tone producing portions of the vibratory strings I It is believed that it will be apparent how the musician may manipulate the knob 48 to create the desired tremolo effect. The spring 50 normally holds the bridge l3 in position against the stop 38 where it is aligned with the stationary bridge l2. The bridge I3 is such that it may be moved or shifted with a minimum amount of friction and with no rattling of the strings II. The roller 33 rotatably supported as above described, is free to turn at will while the bridge is moved in the recess 22. Thus when the bridge (3 is moved in the recess 22 the engagement of the strings H with the roller 33 may cause the roller to turn in a direction opposite to the races 35 and 36.

Figs. 5, 6, and '7 of the drawings, illustrate a form of the invention in which a single movable bridge l3 is provided for the inner ends of the several strings H and may be vibrated or moved to produce tremulous tones. The instrument body I!) may be the same as the body I0 described above, except that its recess 22 is longer to extend transversely below the entire series of strings H. The strings H may be strung in the same manner as in the previously described form of the invention and the instrument may embody an electro-magnetic pick-up l5 of the type described above.

The movable bridge l3 is similar to the bridge l3 except that it is longer to support or form a bridge for the entire set of strings II. The bridge Ili includes a cylindrical roller 33 having axles or trunnions 34 on its opposite ends. Inner races are rotatable on the trunnions 34 and are surrounded by outer races 35 Series of anti-friction balls 3l' are arranged between the races 35 and The outer sides of the races 35" and 3 5 are adapted to cooperate with the side walls of the recess 22 to limit or prevent endwise shifting of the bridge I3 The peripheries of the outer races 36 engage and roll on the inclined bottom wall 23 of the recess 22 The bridge is proportioned to have the tensioned strings H bear on its roller 33 irrespective of its position in the recess 22 A stop 38 of felt or the like is provided at the forward end of the recess 22 to limit the forward movement of the movable bridge l 3 The several vibratory strings ll bear on the single roller d3 and as the bridge l3- is moved in the recess 22 the effective lengths of the strings ii are varied so that a desirable tremolo effect may be produced.

The means M for moving the bridge l3 may be similar to the means l4 described above. A

lever 39 extends horizontally across the series of strings H and has a finger W pivotally supported in an opening iii in the body H). A yoke 43 cooperates with the bridge roller 33*. A finger 44 on the lever 39 pivotally and shiftably cooperates with an opening 65 in the yoke 43 A spring 36 is arranged under compression between the yoke 43 and the lever 39 to hold the yoke 43 in engagement with the roller 33. An operating arm Al projects from the lever 39 and has a handle or knob 48 conveniently engageable by the musician. The knob 43 may be engaged or grasped by the small fin gers of the musicians plucking hand. An arm t9 projects from the lever 38 and a spring 5i! is connected with the arm 39 and the body it to normally hold the bridge l3 against the stop 36. A guard or shield 12 extends over and covers the tremolo producing means of the instrument.

1e body it and extends substantially horizontally over the inner portions of the strings I l and the recesses 22 to enclose the apparatus for creating the tremolo effect. The operating arm M projects forwardly under the shield 72 without interfering with the same.

The operation of the instrument illustrated in Figs. 5 to '7 inclusive of the drawings is substantially the same as that of the previously described form of the invention. If desired, the musician may play the instrument without manipulating the arm 41 in which case the bridge l3 is held against the stop 313" and remains stationary. When it is desired to produce quavering or tremulous tones the knob 48 may be shifted or vibrated back and forth to move the bridge I3 in the recess 22*. This movement of the bridge l3 varies the lengths of the tone producing portions of the strings H to thus create the tremolo effect. Due to the inclination of the bottom of the recess 22 the tension on the strings l I remains substantially constant during the movement of the bridge l3. The single movable bridge i3 may be shifted to create synchronized quavering or trcmulous tones when the several strings ii are vibrated.

Having described only typical preferred forms and applications of my invention, I do not wish to be limited or restricted to the specific details herein set forth, but wish to reserve to myself any variations or modifications that may appear to those skilled in the art or fall within the scope of the following claims.

Having described my invention, I claim:

1. In a musical instrument having a tensioned vibratory string, apparatus for producing tremolo effects comprising, an element having bearing engagement with the string to define its effective tone producing length, an inclined surface supporting the element for compound movement in the direction of the longitudinal axis of the string and the direction of the force exerted on the element by the string, and means for moving the element on said surface.

2. In a musical instrument having a tensioned vibrator string, apparatus for producing tremolo effects comprising, an element having bearing engagement with the string to define its eifective tone producing length, a part having a surface inclined with respect to the longitudinal axis of the string and supporting the element for compound movement in the direction of the longitudinal axis of the string and the direction of the force exerted on the element by the string, and means for moving the element, including a man- The shield 72 is suitably secured to ually operable part operatively associated with the element.

3. In a musical instrument having a tensioned vibratory string, apparatus for producing tremolo effects comprising, an element having bearing engagement with the string to defineits effective tone producing length, a part having a surface inclined with respect to the longitudinal axis of the string and supporting the element for compound movement in the direction of the longitudinal axis of the string and the direction of the force exerted on the element by the string, means normally holding the element stationary, and means for moving the element.

4. In a musical instrument having a tensioned vibratory string, apparatus for producing tremolo effects comprising, a support extending longitudinally of and inclined with respect to the longitudinal axis of the string, a roller having bearing engagement with the string and movable on said support in the direction of the longitudinal axis of the string, and means for moving the roller.

5. In a musical instrument having a tensioned vibratory string, apparatus for producing tremolo effects comprising, a support extending longitudinally of and inclined with respect to the longitudinal axis of the string, a roller having bearing engagement with the string and movable on said support in the direction of the longitudinal axis of the string, spring means holding the roller against movement, and means for moving the roller on the support.

6. In a musicalinstrument, a movable bridge, a tensioned vibratory string bearing on the movable bridge, a support inclined with respect to the longitudinal axis of the string on which the bridge moves back and forth axially of the string, and means for moving the bridge axially of the string to vary the effective length of the string and thereby produce a tremolo effect, said means including, a manual lever, an operative connection between the lever and bridge, and a spring acting on the lever to hold the bridge in a normal position.

7. In a musical instrument, a tensioned vibratory string, a relatively stationary bridge for the string, a part inclined relative to the longitudinal axis of the string, a second bridge for the string shiftably supported on said part, the string having its effective vibratile portion extending between said bridges, and means for moving the second bridge on said inclined part toward and away from the first named bridge to vary the length of said effective portion of the string.

8. In a musical instrument having a tensioned vibratory string, apparatus for producing tremolo effects comprising, a movable element having bearing engagement with the string to define the length of its tone producing portion, means supporting the element for translation longitudinally of the string, and means for shifting the element longitudinally of the string.

9. In a musical instrument having a tensioned vibratory string, apparatus for producing tremolo effects comprising, a movable element having bearing engagement with the string to define the length of its tone producing portion, means supporting the element for translation longitudinally of the string, and a manual actuating part operatively connected with the element for shifting the element longitudinally of the string.

10. In a musical instrument having a tensioned vibratory string, apparatus for producing tremolo effects comprising, a support having a surface extending longitudinally of and inclined with respect to the longitudinal axis of the string, a bridge having bearing engagement with the string and movable along said surface and axially of the string, and means for moving the bridge on the surface axially of the string.

11. In a musical instrument having tensioned vibratory strings, the combination of, a support having a flat surface, a roller movable back and forth on the surface in the direction of the longitudinal axes of the strings and engaged by the strings, and means for moving the roller axially of the strings to produce tremolo effects.

12. In a musical instrument having tensioned vibratory strings, the combination of, a support having a recess, a roller engaging the strings, anti-friction means supporting the roller in the recess for movement therein in the direction of the longitudinal axes of the strings, and means for moving the roller axially of the strings to vary the effective lengths of the strings.

13. In a musical instrument having tensioned vibratory strings, the combination of, a stationary support having a supporting surface, a roller movable to and fro along the surface axially of the string and engaged by the strings to act as a bridge therefor, and means for moving the roller axially of the strings to produce tremolo effects, said means including a manual lever, and a yoke cooperating with the roller and movable by the lever.

14. A musical instrument comprising, a body having a recess, tensioned strings on the body extending over the recess, a roller movable back and forth on the bottom wall of the recess and engaging the strings to form a bridge therefor, the side walls of the recess guiding the roller for such movement, and means for moving the roller axially of the strings to produce tremolo effects.

15. A musical instrument comprising, a body having a recess, tensioned strings on the body extending over the recess, a bridge for the strings movable back and forth in the recess axially of the strings to change the effective lengths of the strings, the side walls of the recess guiding the roller for such movement, spring means normally holding the bridge against movement, and means for moving the bridge axially of the strings to produce tremolo effects.

GEORGE D. BEAUCHAMP. 

